(1) Field of the Invention
The present invention relates to an apparatus and method for coloring an electric wire that includes an electrically conductive core wire and an electrically insulating coating for coating the core wire.
(2) Description of the Related Art
Various electronic devices are mounted on a motor vehicle as a mobile unit. Therefore, the motor vehicle is provided with a wiring harness for transmitting power from a power source and control signals from a computer to the electronic devices. The wiring harness includes a plurality of electric wires and connectors attached to an end of the wires.
The wire includes an electrically conductive core wire and a coating made of insulating synthetic resin, which coats the core wire. The wire is a so-called coated wire. A connector includes a terminal fitting and a connector housing that receives the terminal fitting therein. The terminal fitting, consisting of electrically conductive sheet metal or the like, is attached to an end of the wire and electrically connected to the core wire of the wire. The connector housing made of electrically insulating synthetic resin is formed in a box-shape. When the connector housing is connected to the electronic devices, each wires is connected to the corresponding electronic device through the terminal fitting, thereby the wiring harness transmits the desired electric power and signals to the electronic devices.
When the wiring harness is assembled, first the wire is cut into a specific length and then the terminal fitting is attached to an end of the wire after removing the coating near the end. A wire is connected to another wire according to the need. Afterward, the terminal fitting is inserted into the connector housing, thereby assembling the wiring harness.
The wire of the wiring harness must be distinguished in terms of the size of the core wire, the material of the coating (concerning with alteration in the materials depending upon heat-resisting property), and a purpose of use. The purpose of use means, for example, an air bag, antilock brake system (ABS), control signal such as speed data, and system in a motor vehicle in which the wire is used, such as a power transmission system.
The coating of the wire used in the wiring harness has been colored to a desired color by mixing a coloring agent of the desired color with synthetic resin which constitutes the coating when the synthetic resin of the coating is applied onto the circumference of the core wire by extrusion (for example, see Japanese Patent Application Laid-Open No. H5-111947, Japanese Patent Application Laid-Open No. H6-119833, and Japanese Patent Application Laid-Open No. H9-92056). In this case, when a color of an outer surface of the wire is altered, it is necessary to halt an operation of an extrusion apparatus that performs the extrusion-coating. That is, whenever the color of the wire is changed, it is necessary to halt an operation of an extrusion apparatus, causing increasing in a time period and labor hour required for the production of the wire and deteriorating in the productivity of the wire.
Alternatively, the coloring agent to be mixed has been replaced while the extrusion apparatus is performing the extrusion-coating. In such a case, right after changing the color of the coloring agent, a wire, in the color of the synthetic resin of which a coloring agent before the replacement and a coloring agent after the replacement are mixed, has been inevitably manufactured, causing the deterioration in the yield of the material of the wire.
In order to prevent the deterioration in the productivity of the wire and in the yield of the material of the wire, the present applicant proposed a method, in which monochromatic wire is produced, then the outer surface of the wire is colored with a desired color according to the need, thereby assembling a wiring harness (see Japanese Patent Application No. 2001-256721). Alternatively, the present applicant proposed an apparatus for coloring a wire, by which upon coloring a monochromatic wire, a liquid coloring agent is spouted toward the outer surface of the wire with a specific amount thereof per spouting so as to allow the liquid drop of the coloring agent to adhere to the outer surface of the wire, thereby coloring the wire with the desired color (see Japanese Patent Application No. 2002-233729).
The coloring apparatus described above includes a coloring nozzle that spouts the liquid coloring agent toward the outer surface of the wire with a specific amount thereof per spouting. The coloring nozzle includes a receiver for receiving the coloring agent under pressure, a cylindrical nozzle member that communicates with the receiver and guides the coloring agent therethrough, and a valve element provided in the receiver, which can approach and leave a base end of the coloring nozzle.
In the coloring apparatus for coloring the wire, the coloring agent is spouted from an end of the nozzle member toward the outer surface of the wire in a state that the valve element leaves away from the nozzle member. Further, in the coloring apparatus for coloring the wire, the valve element approaches the nozzle member so as to come in contact with the nozzle member, thereby halting the spouting of the coloring agent from an end of the nozzle member toward the outer surface of the wire.
As for the coloring apparatus, in which the coloring agent is spouted toward the outer surface of the wire with a specific amount thereof per spouting, when the amount of the liquid drop of the coloring agent is changed, that is, when the area to be colored of the outer surface of the wire is changed, the pressure in the receiver as described above may be changed, or alternatively, the time period when the valve element leaves the base end of the nozzle member may be changed. However, in order to change such a pressure or such a time period, the coloring apparatus is forced to have a complicated mechanism therein, thereby causing an increasing in the cost of the coloring apparatus.